1. Field of the Invention
The invention relates to an optical module. More particularly, the present invention relates to an optical module that is capable of sensing images, and to methods for optically aligning and assembling optical components of the optical module.
2. Description of the Related Art
As shown in FIG. 1, a conventional optical module 1 for an optical input device, such as a scanner, mainly includes a housing unit 11, a light-sensing unit 12, a lens unit 13, and a light-emitting unit 14. The housing unit 11 includes an outer housing 111 and a base 112 coupled to the outer housing 111. The outer housing 111 is formed with a groove 113. The light-sensing unit 12 includes a plurality of light-sensing components 121 aligned on top of the base 112. Each of the light-sensing components 121 is a Complementary Metal Oxide Semiconductor (CMOS) image sensor scanner. The lens unit 13 is embedded in the groove 113 in the outer housing 111 at a position that corresponds to the light-sensing unit 12. The light-emitting unit 14 is disposed in the outer housing 111 at a position corresponding to a glass platform 21, and includes a plurality of light-emitting diodes (LEDs) 141. When the light-emitting diodes 141 provide source light toward an object disposed on the glass platform 21, the source light is refracted, and the refracted light travels through the lens unit 13 along a Z-axis direction toward the light-sensing components 121 so as to be focused into an image. At this time, the light-sensing components 121 sense the light impinged thereon and captures an image of the object.
Since precision of the focus of light onto the light-sensing components 121 is the key to determining the resolution of the above mentioned optical input device, optical alignment between the light-sensing unit 12 and the lens unit 13 needs to be highly precise. Currently, the outer housing 111, the base 112, and the light-sensing unit 12 are assembled in advance. Subsequently, the lens unit 13 is mounted in the groove 113, whose depth is predefined, according to a theoretical value in order to define the relative locations of the lens unit 13 and the light-sensing unit 12. Lastly, the lens unit 13 is secured to the base 112 by means of an adhesive to finish the alignment and assembly of the conventional optical module. However, due to cost considerations, the lens unit 13 of the conventional optical module 1 is mostly assembled manually into the groove 113, while neglecting the tolerance of an optical length of the lens unit 13, which is approximately 400 micron. In addition, the relative positions of the lens unit 13 and the light-sensing unit 12 are mainly determined by the depth of the groove 113 and the optical length of the lens unit 13. Therefore, an overly large tolerance usually leads to optical misalignment, which results in over focus or under focus of the conventional optical module 1 such that the resolution thereof is degraded.